Distributed strain monitoring for downhole tools

Abstract

An apparatus for monitoring strain on a downhole component includes a fiber optic sensor having a length thereof in operable relationship with a downhole component and configured to deform in response to deformation of the downhole component. The fiber optic sensor defines a continuous, distributed sensor. An interrogation assembly is configured to transmit an electromagnetic interrogation signal into the fiber optic sensor and is configured to receive reflected signals therefrom. A processing unit is configured to receive information from the interrogation assembly and is configured to determine a strain on the downhole component during running of the downhole component to depth in a borehole.

What is claimed is: 
     
         1 . An apparatus for monitoring strain on a downhole component, the apparatus comprising:
 a fiber optic sensor having a length thereof in an operable relationship with a downhole component and configured to deform in response to deformation of the downhole component, the fiber optic sensor defining a continuous, distributed sensor;   an interrogation assembly configured to transmit an electromagnetic interrogation signal into the fiber optic sensor and configured to receive reflected signals therefrom; and   a processing unit configured to receive information from the interrogation assembly and configured to determine a strain on the downhole component during running of the downhole component to depth in a borehole.   
     
     
         2 . The apparatus of  claim 1 , further comprising a communication line operatively connecting the fiber optic sensor and the interrogation assembly. 
     
     
         3 . The apparatus of  claim 2 , wherein the communication line is a fiber optic cable. 
     
     
         4 . The apparatus of  claim 1 , wherein the fiber optic sensor is an optical fiber sensor. 
     
     
         5 . The apparatus of  claim 4 , wherein the fiber optic sensor is a distributed fiber optic strain monitoring cable. 
     
     
         6 . The apparatus of  claim 1 , wherein the interrogation assembly is configured as part of the downhole component. 
     
     
         7 . The apparatus of  claim 6 , further comprising a data logger configured to record data from at least one of the interrogation assembly and the processing unit. 
     
     
         8 . The apparatus of  claim 1 , wherein the downhole component is a housing configured to mimic the physical properties of a downhole tool. 
     
     
         9 . The apparatus of  claim 1 , wherein the downhole component is operatively connected to a production string. 
     
     
         10 . The apparatus of  claim 1 , wherein the interrogation assembly is on a ground surface and in operative communication with the fiber optic sensor. 
     
     
         11 . The apparatus of  claim 1 , wherein the fiber optic sensor is disposed along a central axis of the downhole component. 
     
     
         12 . The apparatus of  claim 1 , wherein the processing unit is configured to continuously determine a strain on the downhole component during running of the downhole component to depth. 
     
     
         13 . The apparatus of  claim 1 , wherein the processing unit is configured to periodically determine a strain on the downhole component during running of the downhole component to depth. 
     
     
         14 . The apparatus of  claim 1 , wherein the processing unit is configured to determine a strain on the downhole component at a potential landing site. 
     
     
         15 . The apparatus of  claim 1 , wherein the downhole component is an electrical submersible pump. 
     
     
         16 . A method of monitoring strain on a downhole component, the method comprising:
 disposing a length of an fiber optic sensor in a fixed relationship relative to a downhole component, the fiber optic sensor configured to deform in response to deformation of the downhole component, the fiber optic sensor defining a continuous distributed sensor;   running the downhole component into a borehole to a potential landing site;   transmitting an electromagnetic interrogation signal into the fiber optic sensor during running of the downhole component;   receiving reflected signals from the fiber optic sensor during running of the downhole component; and   determining a strain on the downhole component from the received reflected signal during the running of the downhole component.   
     
     
         17 . The method of  claim 16 , further comprising recording the received reflected signals. 
     
     
         18 . The method of  claim 16 , wherein the determining step occurs in situ. 
     
     
         19 . The method of  claim 16 , wherein the fiber optic sensor is disposed along a central axis of the downhole tool. 
     
     
         20 . The method of  claim 16 , further comprising determining a strain on the downhole component at the potential landing site of the downhole component. 
     
     
         21 . The method of  claim 16 , further comprising transmitting at least one of the received reflected signal and the determined strain to a surface component. 
     
     
         22 . The method of  claim 16 , wherein the determining step occurs continuously during the running of the downhole component. 
     
     
         23 . The method of  claim 16 , wherein the determining step occurs periodically during the running of the downhole component.